The invention relates to a process for manufacturing printed-circuit boards which have rigid and flexible areas or internal layers which have rigid and flexible areas for manufacturing multilayer printed-circuit boards. At least one rigid and at least one flexible layer of insulating material are bonded together sandwich-like by means of compound films; in this arrangement, at least the flexible layer of insulating material carries printed conductors.
Printed-circuit boards of this kind as well as the process for the manufacture thereof are known. Such a process is disclosed in the German publication OS 35 15 549; it determines that in the rigid/flexible transitional areas, the rigid layer of insulating material must be provided with continuous slots before the printing. In order to prevent chemicals and other foreign matter from intruding between the non-bonded rigid and flexible layers of material, these slots are sealed by means of a copper film. After etching the copper film, however, the slots are exposed again such that it is possible again for chemicals to enter during the subsequent process.
Furthermore, there is a risk that the flexible material is not supported in the slot area and it thus can sink into the slot which again leads to problems of low radiant exposure (wrong exposure) during the conductive pattern process. Moreover, laminating a covering film onto the flexible conductor side can cause indentations and even ruptures of the printed conductor in the slot area.